The present invention relates to a liner ring for a pump, and more particularly to a pump liner ring which is provided between a pump casing and an impeller to check counterflow therebetween.
Conventionally, in a centrifugal pump, in order to prevent the liquid discharged out of the impeller from being leaked toward the suction side of the pump casing, there are provided a wearing ring (or impeller ring) on the side of the impeller, and a liner ring (or a casing ring) on the side of the casing in confrontation with the wearing ring. The wearing ring and the liner ring are provided in such a manner that the clearance between the rings is kept small.
Since the wear condition of the liner ring or the wearing ring cannot be easily observed from the outside, wear resisting material must be used for the liner ring or the wearing ring. When a non-corrosive liquid is used in the pump, bronze, cast iron or surface hardened steel or the like is employed as the wear resisting material. On the contrary, when a corrosive liquid is used in the pump, 18Cr-8Ni stainless steel is often employed, but such stainless steel is not effective against wear. Therefore, in this case, the clearance between the rotating member and the stationary member must be larger than the average clearance commonly used.
In addition to the above-mentioned metal for a liner ring, the use of carbon material or Teflon (trademark) material having excellent wear resistance is desirable.
However, carbon material or Teflon material is difficult to handle when it is used in a high temperature environment or the like. That is, since material, such as carbon or Teflon, which is suitable for an annular member has a different thermal expansion coefficient than that of metal used for a pump casing, such material cannot be installed on the pump casing by mean of a force fit which is generally used for liner rings made of metal. Therefore, a housing made of rubber is often used in conjunction with the annular sealing member made of carbon or Teflon, or the usage temperature range of the liner ring is often limited to a certain range.